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fCGDtkmkMgU-009|So silver, when it's reduced, can form oxidized copper.
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fCGDtkmkMgU-012|Silver metal will plate out on to copper.
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fCGDtkmkMgU-014|Now, you could also make gold plate out if you had the correct combination of ions.
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fCGDtkmkMgU-015|So if you said silver or gold in this case, you are correct.
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B-HgZ3G95oA-000|Let's look at the equilibrium situation between liquid water and gaseous water at 25 degrees C.
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B-HgZ3G95oA-001|What can we determine about the free energy difference and K?
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B-HgZ3G95oA-002|Now, here I'm talking about the free energy without the standard sign.
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B-HgZ3G95oA-003|So the free energy difference under the situation that exists right now.
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B-HgZ3G95oA-012|So delta G without the standard state is 0.
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B-HgZ3G95oA-013|It's the free energy difference between these actual concentrations at equilibrium.
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B-HgZ3G95oA-014|So at equilibrium you may remember that the partial pressure of gaseous water is around 0.03 of an atmosphere.
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B-HgZ3G95oA-015|So the free energy difference between gaseous water at 0.03 of an atmosphere and liquid water at 25 degrees C is 0.
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B-HgZ3G95oA-016|K is the equilibrium constant for that value, which is 0.03 of an atmosphere.
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B-HgZ3G95oA-017|So K is less than 1, 0.03, and delta G is 0.
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B-HgZ3G95oA-018|The correct answer here is B.
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KT_N4_kKHnQ-000|Gases are an ideal system to look at energy changes, because gases change their energy in direct proportion to temperature changes.
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KT_N4_kKHnQ-001|Remember, the energy change of a gas is 3/2 RT for one mole, 3/2 nRT for a given number of moles.
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KT_N4_kKHnQ-002|But if the temperature changes, the energy changes.
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KT_N4_kKHnQ-003|So an energy change always corresponds to a temperature change, so the gas is kind of transparent that way.
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KT_N4_kKHnQ-004|It can't hide an energy change because the temperature always changes.
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KT_N4_kKHnQ-005|So when work is done on a gas, that's an energy change and could be reflected in a temperature change.
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KT_N4_kKHnQ-006|If heat is absorbed by gas, that's an energy change, could be reflected in the temperature change.
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KT_N4_kKHnQ-009|So I have to keep track of both the heat and the work to manage energy changes.
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KT_N4_kKHnQ-010|Let's look at the work.
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KT_N4_kKHnQ-011|If I do work for a gas, I push a cylinder up in a gas, I change the height of this cylinder.
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KT_N4_kKHnQ-012|Work is just force times distance, or in this case, force times the height.
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KT_N4_kKHnQ-016|If I expand, the system is also doing the work, and that should take some of the system's energy to do that work.
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KT_N4_kKHnQ-020|If a gas is compressed, then I do work on the gas.
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KT_N4_kKHnQ-023|I'm the surroundings, the system is the gas, I compress it, the energy of the system tends to go up, work is positive in those circumstances.
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KT_N4_kKHnQ-024|So that's how work, the change in volume, and external pressure are involved in calculating energy changes for gases.
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V-FBHIdXk20-000|Let's look at the hydrogen-like energy systems.
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V-FBHIdXk20-001|Now when I say hydrogen-like, I mean the one-electron systems.
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V-FBHIdXk20-002|Hydrogen, a proton and an electron, that's a complete hydrogen atom.
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V-FBHIdXk20-004|Or you could go lithium plus 2.
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V-FBHIdXk20-005|As you have one-electron systems, they all behave just like hydrogen atoms.
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V-FBHIdXk20-006|So let's look at those.
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V-FBHIdXk20-007|Which ion does the energy-level diagram X correspond to?
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V-FBHIdXk20-008|So here's hydrogen and near it, some unknown ion, X.
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V-FBHIdXk20-019|Here we have hydrogen and some other ion.
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V-FBHIdXk20-020|Now, what lines up here?
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V-FBHIdXk20-021|We know that the energies go as minus Z squared over n squared.
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V-FBHIdXk20-022|And we see in this system that level 2 in the unknown system lines up with level 1 in the hydrogen system.
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V-FBHIdXk20-023|And that energy 1 for this system is 1 squared over 1 squared times i infinity.
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V-FBHIdXk20-024|That's the hydrogen atom.
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V-FBHIdXk20-025|For this one, it has to be something over something to still give me minus R infinity.
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V-FBHIdXk20-026|The value of Z is undetermined here because we don't know which ion it is.
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V-FBHIdXk20-027|But the value of n is 2.
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V-FBHIdXk20-031|So if it has two protons-- I don't care what else it has in it-- it is a helium nucleus.
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V-FBHIdXk20-032|So a helium plus is the ion that would have this configuration on its electronic energy scale.
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V-FBHIdXk20-033|Z will be 2 for helium.
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z76W5579a5Y-000|The decomposition of hydrogen peroxide, H2O2, is exothermic.
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z76W5579a5Y-001|Now, if you look carefully at this reaction, what can you determine about the structure of H2O2 simply knowing that that reaction is exothermic?
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z76W5579a5Y-012|So energetically, that doesn't tell us anything about whether this reaction is endothermic or exothermic.
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z76W5579a5Y-013|What about the oxygen bond?
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z76W5579a5Y-014|On this side, I'm forming oxygen gas, so O2 double-bonded.
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z76W5579a5Y-015|And I form half a mole of those.
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z76W5579a5Y-016|On this side, I have to break a mole of oxygen-oxygen bonds.
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z76W5579a5Y-017|The question is, are they double bonds or single bonds?
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z76W5579a5Y-019|And we know it's not endothermic, so we can already rule out C and B.
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z76W5579a5Y-020|Now, what about if it's a single bond?
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z76W5579a5Y-022|That is, the double bonds have to be more than twice as energetic to be stable as the single bonds.
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z76W5579a5Y-025|So that will give us a net exothermic reaction, and the correct answer here is A, the single-bonded structure.
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1iUgRsNvJkA-000|The isomerisation of propanol to isopropanol is endothermic.
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1iUgRsNvJkA-001|Now what does that tell you about burning propanol and isopropanol?
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1iUgRsNvJkA-002|Which burns cooler?
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1iUgRsNvJkA-010|Propanol and isopropanol both burn in oxygen to form carbon dioxide in water.
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1iUgRsNvJkA-011|And they are the same chemical formula, but different structure.
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1iUgRsNvJkA-012|They're structural isomers.
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1iUgRsNvJkA-013|Does that structurally isomerisation cause a different enthalpy of burning?
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1iUgRsNvJkA-018|But they go to the same products.
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1iUgRsNvJkA-019|So isopropanol burning to give the same products this same state is a greater drop in enthalpy.
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1iUgRsNvJkA-020|So there's a greater release in energy on the burning of isopropanol.
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1iUgRsNvJkA-021|So propanol burns cooler.
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1iUgRsNvJkA-022|The correct answer here is A.
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qpmTRXIJhFo-000|When we talk about ionization energy, we're talking about how easy is it to remove an electron from an atom?
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qpmTRXIJhFo-001|Well, what holds the electron about the atom?
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qpmTRXIJhFo-002|It's the positive charge on the nucleus.
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qpmTRXIJhFo-003|So the more positive charge that an electron can see, the more difficult it is to ionize.
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qpmTRXIJhFo-004|And by contrast, the more of that charge that's shielded, the easier it is to remove that electron.
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qpmTRXIJhFo-005|And easier to remove means higher energy.
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qpmTRXIJhFo-006|Those energy levels go up closer to the 0 state.
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qpmTRXIJhFo-007|Remember, the 0 state for the nucleus and the electron is the ionized state.
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qpmTRXIJhFo-008|So you get closer to the ionized state, the more charge you can shield from outer electrons.
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qpmTRXIJhFo-009|Let's look at that.
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qpmTRXIJhFo-010|So if we have electrons, hydrogen and helium plus, those are both one electron systems, and they're very easy to understand.
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qpmTRXIJhFo-011|Their ionization energy will just be z squared-- the charge on the nucleus-- over n-- whichever orbital the electron happens to be in.
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qpmTRXIJhFo-013|And that's identically four times that.
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qpmTRXIJhFo-014|They're one electron systems.
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qpmTRXIJhFo-015|The charge on the nucleus is plus 2 for helium.
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qpmTRXIJhFo-016|Plus 2 squared is 4, so you have four times the ionization energy for helium, as opposed to hydrogen.
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qpmTRXIJhFo-017|Now, what if you start to put some electrons in the helium?
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qpmTRXIJhFo-018|We can look at helium in the 1s2 state.
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qpmTRXIJhFo-020|If it's sufficient to ionize, the electrons will be ejected.
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qpmTRXIJhFo-021|And if you put even more energy in, that electron goes-- that energy goes into kinetic energy of the electron.
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qpmTRXIJhFo-022|So let's go ahead and look at helium in the 1s2 state.
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qpmTRXIJhFo-023|Now the electric ionization energy is given by the effective charge squared over n squared.
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qpmTRXIJhFo-026|Well, the answer is no.
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qpmTRXIJhFo-027|Two s electrons don't shield each other fully.
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qpmTRXIJhFo-029|So the s electrons-- there's a little bit of shielding going on, but it's not a full nuclear charge that shielded.
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qpmTRXIJhFo-030|How about if one of those electrons is promoted, is excited, out to a 2 state, the 2p, for instance?
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